Electrical fuel injection control system for internal combustion engines

ABSTRACT

A system for electrically controlling the fuel injection in a multi-cylinder internal combustion engine comprising a first fuel injection starting signal generator for generating a first starting signal defining the fuel injection starting timing for a specific cylinder, a second fuel injection starting signal generator for generating second starting signals defining the fuel injection starting timing for the individual cylinders, a fuel injection duration signal generator for generating a fuel injection duration signal for the specific cylinder in response to the application of at least the first starting signal, a fuel injection ending signal generator coupled with the second starting signal generator and said duration signal generator for initiating fuel injection ending timing for the individual cylinders, the ending signals appearing after the occurrence of the starting signals and while the duration signals are activated, a fuel injection ending signal distributor for distributing said ending signals to the individual cylinders taking each ending signal corresponding to the specific cylinder as a reference, and a fuel injection starting signal distributor for distributing the second starting signals to each of the individual cylinders taking said first starting signal as a reference.

United States Patent 11 1 Oishi et al. v

1 1 June 24, 1975 1 ELECTRICAL FUEL INJECTION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES [75] Inventors: Kazuo Oishi; Noriyoshi Ando;

Hiroshi Yoshida, all of Kariya, Japan ['73] Assignee: Nippondenso Co., Ltd., Kariya.

Japan [22] Filed: Apr. 19, 1973 [21] Appl. No.: 352,697

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 97,880, Dec. 14,

1970, abandoned.

[52] U.S. Cl... 123/32 EA; 123/119 R; 123/140 MC [51] Int. Cl. F02b 3/00 [58] Field of Search 123/32 EA, 119, 139 AW,

[56] References Cited UNITED STATES PATENTS 2,867,200 1/1959 Grydcn et al 123/32 EA 2,918,911 12/1959 Guiot 123/32 EA 3,456,628 7/1969 Bassot et a1. 123/32 EA 3,522,794 8/1970 Reichardt 123/32 EA 3,526.212 8/1970 Bassot et a1. 123/32 EA 3,612.011 10/1971 Monpetit 123/32 EA sTmfcmlv smRr/A/a m SIGAML 4 GENERATOR JANET/av l/a DURATION SIGNAL GENE/470R 2A0 40 4b START/A6 S/GNAL Primary ExaminerCharles .1. Myhre Assistant Examiner-Ronald E. Cox Attorney, Agent, or Firm-Cushman, Darby &

vCushman 5 7 ABSTRACT A system for electrically controlling the fuel injection in a multi-cylinder internal combustion engine comprising a first fuel injection starting signal generator for generating a first starting signal defining the fuel injection starting timing for a specific cylinder, a second fuel injection starting signal generator for generating second starting signals defining the fuel injection starting timing for the individual cylinders, a fuel injection duration signal generator for generating a fuel injection duration signal for the specific cylinder in response to the application of at least the first starting signal, a fuel injection ending signal generator coupled with the second starting signal generator and said duration signal generator for initiating fuel injection ending timing for the individual cylinders, the ending sig nals appearing after the occurrence of the starting signals and while the duration signals are activated, a fuel injection ending signal distributor for distributing said ending signals to the individual cylinders taking eacl ending signal corresponding to the specific cylinder as a reference, and a fuel injection starting signal distributor for distributing the second starting signals to each of the individual cylinders taking said first starting signal as a reference.

22 Claims, 76 Drawing Figures I M/E C 77011 STAFF/V6 SIGNAL ENEPATOI? PATENTEIJJUN24 I975 3 8 90 3,8

SHEET 7 FIG /50 f f OUTPUT AT Ourpumr OUTPUT AT PATENTEDJUN24 I975 3.890.938

SHEET 8 OUTPUT/17' I 90 F/G /8b K OUTPUT AT OUTPUT AT OUTPUT AT FIG /9 new /005b 00711 V 9 H00 H9 ELECTRICAL FUEL INJECTION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending US Pat. application Ser. No. 97,880 filed Dec. 14, I970 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an electrical fuel injection control system for a multi-cylinder internal combustion engine for electrically controlling the injection of fuel into the individual cylinders of the engine.

2. Description of the Prior Art In a conventional electrical fuel injection control system for a multi-cylinder internal combustion engine, electromagnetic or solenoid operated valves are successively urged to the open position to inject fuel under constant pressure into the cylinders through the associated nozzles, and the amount of injected fuel is determined by the length of time during which each individual solenoid operated valve is kept in its open position, that is, the length of time during which current is supplied to the solenoid operated valve. However, in the range in which the multi-cylinder engine is rotating at A high speed, it frequently occurs that the current supply to the solenoid operated valve associated with the next cylinder is started while the current is being supplied to the solenoid operated valve associated with the preceding cylinder. It has therefore been the common practice to inject fuel into a few cylinders at the same time in a high speed rotation range of the engine or to employ a plurality of fuel injection duration signal generators generating a fuel injection duration signal for urging the solenoid operated valves to their open position sequentially. However, the injection of fuel into a few cylinders at the same time is undesirable for the satisfactory operation of the engine because the operating timing of the suction valves of some cylinders may not be in accord with their fuel injection timing. Thus, from the viewpoint of the acceleration characteristic, etc. of the engine, this method has a serious defect in that it is inferior to the method of sequentially distributing the fuel into individual cylinders with properly controlled timing. The system employing a plurality of fuel injection duration signal generators is also defective in that the signal generators must be regulated so as to deliver the same signal of the same duration and it is extremely difficult to regulate the fuel injection duration signal generators for the respective cylinders to suit the above demand over the entire driving conditions.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrical fuel injection control system for a multicylinder internal combustion engine which includes a single fuel injection duration signal generator for equalizing the duration of fuel injection for the individual cylinders and injecting fuel with appropriate timing into the individual cylinders so that the fuel injection duration signal itself can be distributed to the cylinders in a low speed rotation range of the engine, while in a high speed rotation range of the engine where the period of time of fuel injection for one cylinder may overlap that of another cylinder, a plurality of fuel injection duration signals for the respective cylinders are produced on the basis of the signal generated by the single fuel injection duration signal generator and are distributed to the fuel injection means associated with the respective cylinders thereby to solve the problem of nonuniformity of the duration of fuel injection for the individual cylinders, to make it possible to inject the fuel into the cylinders with different timing, and to eliminate undesirable pulsation of the fuel pressure and electrical outputs.

Another object of the present invention is to provide an electrical fuel injection control system for a multicylinder internal combustion engine in which, in a low speed rotation range of the engine where it is difficult to produce a plurality of fuel injection duration signals. on the basis of the fuel injection duration signal the fuel injection duration signal generator produces a fuel injection timing signal to be distributed to the individual cylinders so that the engine can accurately operate even in the low speed range.

In accordance with the present invention, there is provided an electrical fuel ignition control system for a multi-cylinder internal combustion engine for electrically controlling the injection of fuel into the individual cylinders comprising a first fuel injection starting signal generator for generating a first fuel injection starting signal defining the fuel injection starting timing for a specific cylinder among the cylinders, a second fuel injection starting signal generator for generating a second fuel injection start ing signal for the individual cylin ders, a fuel injection duration signal generator for g n erating at least one for the specific sylinder of fuel injection duration signals for the individual cylinders conforming to a required duration of fuel injection in response to the application of at least one for the specific cylinder of the fuel injection starting signals, a fuel injection ending signal generator for generating a fuel injection ending signal for the individual cylinders in response to the application of said fuel injection duration signal and said second fuel injection starting signal, a fuel injection ending signal distributor for distributing said fuel injection ending signal to the fuel injection means associated with the individual cylinders taking said first fuel injection starting signal as a reference, and a fuel injection starting signal distributor for distributing said second fuel injection starting signal to said fuel injection means associated with the individual cylinders taking said first fuel injection starting signal as a reference, said system further comprising as required a first discriminator for applying to said fuel injection duration signal generator a signal corresponding to the fuel injection starting signal generated by said second fuel injection starting signal generator when the speed of the engine is lower than a predetermined speed so that said fuel ignition duration signal generator generates a fuel injection duration signal for the individual cylinders, and a second discriminator for producing a fuel injection ending signal for the individual cylinders directly from the fuel injection duration signal generated by said fuel injection duration signal generator in the low speed range so that said fuel injection ending signal distributor distributes the fuel injection ending signal to the individual cylinders.

The present invention having the features set forth in the above provides the following advantages:

1. The provision of only one fuel injection duration signal generator is advantageous over a conventional system including a plurality of fuel injection duration signal generators in that the duration of fuel injection for the individual cylinders is free from any fluctuation and is uniform.

2. In a high speed range of the engine in which the period of time of fuel injection for one cylinder may overlap that of another cylinder. a fuel injection ending signal for the individual cylinders is newly produced on the basis of the fuel injection duration signal for a predetermined specific cylinder. Thus. an appropriate amount of fuel can be sequentially injected into the individual cylinders with optimum fuel injection timing in such a high speed range. As a result. the engine can fully develop its output and any undesirable pulsation of pressure applied to the fuel as well as electrical pulsation can be reduced to a minimum.

3. In a low speed range of the engine, the single fuel injection duration signal generator generates a fule injection duration signal for the individual cylinders in accordance with the instructions given by the first discriminator, and this signal is applied to the second discriminator to be distributed to the individual cylinders by way of the fuel injection ending signal distributor. Thus, the fuel injection can be accurately carried out even in a very low speed range such as when the engine is started from the non-operative condition.

By virture of the above advantages, an ideal fuel injection characteristic can be obtained throughout the entire operating conditions of the engine ranging from the starting to its maximum speed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an electrical circuit diagram of a fuel injection starting signal generator for a specific cylinder.

FIGS. 3a through 3fshow voltage waveforms appearing at various parts of the circuit shown in FIG. 2.

FIG. 4 is an electrical circuit diagram of a fuel injection starting signal generator for the individual cylinders.

FIGS. 5a through 5c show voltage waveforms appearing at various parts of the circuit shown in FIG. 4.

FIG. 6 is an electrical circuit diagram of a fuel injection duration signal generator.

FIGS. 7a through 70 show voltage waveforms appearing at various parts of the circuit shown in FIG. 6.

FIG. 8 is a block diagram of a fuel injection ending signal generator.

FIGS. 9 through 11 are electrical circuit diagrams of various electrical circuits shown by the blocks in FIG. 8.

FIGS. 12a through l2e show voltage waveforms appearing at various parts of the circuits shown in FIGS. 9 through 11.

FIG. 13 is an electrical circuit diagram ofa fuel injection ending signal distributor.

FIGS. 14a and 141; show waveforms of inputs applied to the circuit shown in FIG. 13.

FIGS. 15a through 15d show waveforms of outputs delivered from the circuit shown in FIG. 13.

FIG. 16 is an electrical circuit diagram ofa fuel injection starting signal distributor.

FIGS. 17a and 17b show the waveforms of inputs applied to the circuit shown in FIG. 16.

FIGS. 18a through 18d show the waveforms of outputs delivered from the circuit shown in FIG. 16.

FIG. 19 is an electrical circuit diagram ofa fuel injection circuit.

FIGS. 20a through 20/1 show waveforms of inputs applied to the fuel injection circuit from the fuel injection ending signal distributor and fuel injection starting signal distributor.

FIGS. 21a through 21m show voltage waveforms appearing at various parts of the fuel injection circuit shown in FIG. 19.

FIGS. 22a through 22m show voltage waveforms appearing at various parts of the fuel injection circuit shown in FIG. I9 when the duration of fuel injection is varied.

FIG. 23 is a block diagram of another embodiment of the present invention. I

FIG. 24 is an electrical circuit diagram of a first discriminator.

FIG. 25 is an electrical circuit diagram of a second discriminator.

FIG. 26 is an electrical circuit diagram of a third discriminator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 which shows a block diagram of an embodiment of the present invention, a fuel injection starting signal generator 1 generates a signal representing the fuel injection starting timing for a predetermined specific cylinder which may, for example, be the first cylinder of a four-cylinder internal combustion engine. Another fuel injection starting signal generator 2 generates a signal representing the fuel injection starting timing for the individual cylinders. In response to the application of the fuel injection starting signal from the fuel injection starting signal generator 1 for the specific cylinder, a fuel injection duration signal generator 4 generates a fuel injection duration signal having a pulse width which is in accord with the duration of fuel injection for the specific cylinder. The fuel injection starting signal for the individual cylinders delivered from the fuel injection starting signal generator 2 and the fuel injection duration signal for the specific cylinder delivered from the fuel injection duration signal generator 4 are applied to a fuel injection ending signal generator 6 which produces, on the basis of the fuel injection duration signal applied thereto, fuel injection ending signals instructing the end of the fuel injection into the indivudual cylinders sequentially. A fuel injection ending signal distributor 8 distributes the fuel injection ending signals to the individual cylinders in response to the application of the signals from the fuel injection ending signal generator 6. A fuel injection starting signal distributor 9 distributes the fuel injection starting signal to the individual cylinders in response to the application of the fuel injection starting signal for the individual cylinders from the fuel injection starting signal generator 2 and the fuel injection starting signal from the fuel injection starting signal generator 1 for the specific cylinder. The fuel injection starting signal and the fuel injection ending signal for the individual cylinders are applied to a fuel injection circuit 10 which includes means for energizing and de-energizing the solenoid operated valves associated with the respective cylinders. An inverter 12 is connected between the fuel injection starting signal generator 2 and the injection starting signal distributor 9, and also another inverter 13 between the injection ending signal generator 6 and the injection ending signal distributor 8.

The fuel injection starting signal generator 1 for the specific cylinder may be composed of means incorporated in the ignition signal distributor for detecting a predetermined position during the operating cycle of the specific cylinder which is herein the first cylinder and a wave shaping circuit for subjecting the output from the detecting means to wave shaping. The operating position of the specific cylinder can be detected by a method in which a signal responsive to the operation of the specific cylinder has a special shape or magnitude or a method in which a signal is produced solely at the fuel injection starting timing of the specific cylinder. In the former case, a generator may generate a higher voltage in response to the operation of the specific cylinder than when the remaining cylinders are in operation. In the latter case, a switch which is urged to open or close at the fuel injection starting timing of the specific cylinder may be employed. The wave shaping circuit may include a suitable combination of an amplifier, a Schmitt circuit and a differentiator for detecting the fuel injection starting timing of the specific cylinder.

A practical circuit diagram of the fuel injection starting signal generator 1 for the specific cylinder is shown in FIG. 2. Referring to FIG. 2, a signal generator G is mounted rotatably in synchronism with rotation of the engine (not shown) for producing a signal responsive to the operating position of the specific cylinder. The signal generator G, is connected to a Schmitt circuit which includes an input resistor 101, bias resistors 102 and 103, a pair of transistors 104 and 107, a load resistor 105 for the transistor 104, a coupling resistor 106, a resistor 108 for determining a Schmitt level L shown in FIG. 3a, a common emitter resistor 109 for the transistors 104 and 107, and a load resistor 110 for the transistor 107. A capacitor 111 and a resistor 112 constitute a differentiator. An amplifying transistor 113 is connected to the differentiator and has a load resistor 114. A resistor 121 in combination with capacitor 220 as shown in FIG. 4 acts to differentiate and produce a synchronizing signal Sy, described later, which appears at input terminal 1a. A transistor 122 and a silicon controlled rectifier 123 constitute a flip-flop circuit which has a load resistor 124 connected therewith. A capacitor 125 and a resistor 126 constiture a differentiator which is connected to an output terminal 1b through a coupling capacitor 127.

In operation, the signal generator G generates a signal having a waveform as shown in FIG. 3a at the start of the fuel injection for the specific cylinder. When no signal is applied from the signal generator G to the Schmitt circuit composed of the circuit elements 101 through 110, the transistor 104 is cut off and the transistor 107 is conducting by the biasing action of the resistors 101, 102 and 103. Then, when the signal generated by the signal generator G, attains a positive level above the Schmitt level L,. the transistor 104 conducts and the transistor 107 is cut off. As the angular position of rotation of the engine crankshaft is further advanced until the voltage level of the signal generated by the signal generator G becomes lower than the Schmitt level L, again, the transistor 104 is cut off and the transistor 107 conducts again with the result that a rectangular waveform appears across the resistor 110. FIG. 3b shows such a voltage waveform appearing at point B.

Although, actually, there is a slight hysteresis in the action of the Schmitt circuit, the hysteresis is not taken into consideration herein since it is negligible. This rectangular waveform is then differentiated by the differentiator composed of the capacitor 111 and the resistor 112 so that a waveform as shown in FIG. 30 appears at point C. The negative pulse appearing at point C is amplified and inverted in polarity by the transistor 113. The collector of the transistor 113 is connected to the gate of the silicon controlled rectifier 123, which is therefore urged to conduct by the positive pulse obtained by the amplification and polarity inversion of the negative pulse. When a negative pulse Sy (which is described hereafter) shown in FIG. 3d is applied to the input terminal la with the further rotation of the cngine crankshaft, the transistor 122 is cut off thereby to turn off the silicon controlled rectifier 123. As a result, a voltage waveform as shown in FIG. 32 appears at point E. This waveform is differentiated by the differentiator composed of the capacitor 125 and the resistor 126 so that an output signal as shown in FIG. 3f appears at point F. This output signal appears through the capacitor 127 at the output terminal lb to be applied to the fuel injection duration signal generator 4 and fuel injection starting signal distributor 9.

The structure of the second fuel injection starting signal generator 2 may be similar to that of the first fuel injection starting signal generator 1 for the specific cylinder. Thus, the second fuel injection starting signal generator 2 may include means such as a signal generator or breaker point generating a signal at the fuel injection timing of the individual cylinders and a wave shaping circuit for accurately detecting the fuel injection starting timing of the individual cylinders as in the case of the fuel injection starting signal generator 1 for the specific cylinder.

Referring to FIG. 4, a signal generator G which is mounted rotatably in synchronism with rotation of the engine (not shown), generates a voltage signal having a waveform as shown in FIG. 5a at the fuel injection starting timing of the individual cylinders and is connected to a Schmitt circuit composed of an input resistor 210, bias resistors 211 and 212, a pair of transistors 217 and 218, a load resistor 213 for the transistor 217, a coupling resistor 214, a common emitter resistor 215, a resistor 216 for determining a Schmitt level L shown in FIG. 5a, and a load resistor 219 for the transistor 118. In the Schmitt circuit, the transistor 217 is cut off at the Schmitt level L; from the previous conducting state and therefore the transistor 218 is urged to conduct from the previous cut-off state with the result that an output having a rectangular waveform as shown in FIG. 5b is delivered from the Schmitt circuit. The resistor 216 is suitably selected to provide the Schmitt level L described above. Since it is preferable that a sufficient triggering action can be ensured even when the waveform of the output from the signal generator G has a small amplitude and that the level L is desirably as close to the zero as possible in order to accurately detect a reference position 6 the resistors 210, 211, 212, 214, 215 and 216 are designed to suit the above purpose. The output from the Schmitt circuit is differentiated by a differentiator composed of a capacitor 220 and a resistor 121 as shown in FIG. 2 so that negative pulses Sy appear in synchronism with angular positions 0 0 6 as shown in FIG. 50. The output pulse S appears through the differentiator capacitor 220 at an output terminal 2a to be applied therefrom to the fuel injection starting signal generator 1 for the specific cylinder, fuel injection ending signal generator 6 and fuel injection starting signal distributor 9.

Referring to FIG. 6 showing an electrical circuit diagram of the fuel injection duration signal generator 4, it comprises a saw-tooth wave resetting transistor 400, a bias resistor 401 for the transistor 400, a capacitor 402 across which a saw-tooth waveform appears, a resistor 403 for determining a fixed time constant of the saw-tooth waveform appearing across the capacitor 402, an amplifying transistor 404 of an emitter follower configuration, a load resistor 405 for the emitter follower transistor 404, a reference voltage generator 406 generating a reference voltage corresponding to the amount of injected fuel required by the engine, a comparator and rectangular wave generator 407 (hereinafter to be referred to merely as a comparator), a coupling resistor 408, an amplifying transistor 409, a load resistor 410 for the transistor 409, a feedback resistor 411, a signal input terminal 4a, and a signal output terminal 4b.

In operation, the transistor 400 conducts in response to the application of the signal or a pulse V, as shown in FIG. 7a from the fuel injection starting signal generator l for the specific cylinder to the input terminal 4a. Upon conduction of the transistor 400, the charge stored in the capacitor 402 is discharged across the collector and emitter of the transistor 400. Since the pulse V, applied to the base of the transistor 400 lasts for a very short period of time, the completely discharged capacitor 402 is recharged soon. Voltage waveforms appearing at various parts of the generator 4 are shown in FIGS. 7a through 7c. The input pulse signal V, having a waveform as shown in FIG. 7a is applied to the input terminal 4a, thence to the base of the transistor 400 at time t The transistor 400 conducts to cause the capacitor 402 to discharge and a voltage V, varying in a manner as shown in FIG. 7b appears across the capacitor 402. The input pulse V, disappears soon and the capacitor 402 is charged through the resistor 403 again. The capacitor 402 discharges through the transistor 400 in response to the application of the next input pulse V, to the input terminal 4a at time 1 Thus, a saw-tooth waveform V, having a fixed gradient determined by the capacitance of the capacitor 402 and the resistance of the resistor 403 appears across the capacitor 402 as shown in FIG. 7b. The voltage across the capacitor 402 appears across the resistor 405 through the transistor 404 to be applied to one of the input terminals of the comparator 407. On the other hand, a reference voltage V, corresponding to the amount of injected fuel required by the engine is applied to the other input terminal of the comparator 407 in which this reference voltage V is compared with the sawtooth waveform V,,. As a result, a rectangular waveform S, as shown in FIG. 7c appears at the output terminal of the comparator 407, and has a pulse width 1; ranging from time 1,, at which the saw-tooth waveform V, starts to rise to time t, at which the voltage level of the reference voltage V, is equal to that of the sawtooth waveform V,,. This rectangular waveform S, is applied through the resistor 408 to the transistor 409 to be amplified thereby and appears across the resistor 410. Since the time constant of the saw-tooth waveform V, is fixed, the pulse width t, of the rectangular pulse S, is determined depending on the level of the reference voltage V, When especially the fixed time constant of the saw-tooth waveform V, is sufficiently large compared with the pulse width (duration of fuel injection) t shown in FIG. 7c, the pulse width [[Of the rectangular waveform S, representing the duration of fuel injection is approximately proportional to the reference voltage V The purpose of the feedback resistor 411 is to prevent the rectangular waveform S, from undesirable fluctuation which may occur at time 1, due to noises or any other causes. In this manner, a rectangular waveform signal having a pulse width t, which is in accord with the required duration of fuel injection can be derived from the output terminal 4b of the fuel injection duration signal generator 4.

The duration of fuel injection for one of the cylinders would not overlap the duration of fuel injection for another cylinder when the number of revolutions of the engine is low. When, however, the engine rotates at high speed and the load on the engine is large, a large amount of fuel is required in one cycle of the engine, and to meet this requirement, current must be supplied for an extended period of time to the solenoid operated valves supplying fuel to the engine. However, the single fuel injection duration signal generator 4 cannot satisfactorily function in a situation in which the injection of fuel into the next cylinder takes place before the injection of fuel into preceding cylinder is not finished, that is, an overlap occurs in the period of time of fuel injection. In such a situation, especially in a high speed range of the engine operation, a fuel injection duration signal which is the same as the fuel injection duration signal for the specific cylinder must be produced with a predetermined time lag or in an out-of-phase relationship. The function is attained by the fuel injection ending signal generator 6 which produces, on the basis of the fuel injection duration signal for the specific cylinder delivered from the fuel injection duration signal generator 4, a signal instructing the end or termination of fuel injection into all the cylinders except for the specific cylinder.

Referring to FIG. 8 showing a block diagram of the fuel injection ending signal generator 6, it comprises a saw-tooth wave generator 60, a detector 63 for detecting the end of the fuel injection duration signal for the specific cylinder supplied from the fuel injection duration signal generator 4, and an imitative signal generator 66 for producing a signal instructing the end of fuel injection into all the cylinders except for the specific cylinder on the basis of a signal delivered from the detector 63, that is, on the basis of the end of the fuel injection duration signal for the specific cylinder. The fuel injection starting signal Sy for the individual cylinders delivered from the fuel injection starting signal generator 2 issupplied to the saw-tooth wave generator 60 as a resetting signal so that the saw-tooth wave generator 60 generates a saw-tooth waveform of constant peakmagnitude which is independent of the number of revolutions per unit of time of the engine. In response to the delivery of the signal from the detector 63 which detects the end of the fuel injection duration signal for the specific cylinder supplied from the fuel injection duration signal generator 4, the imitative signal generator 66 stores therein the memory of the level of the saw-tooth waveform at that moment. Then, when the saw-tooth waveform attains the specific level again, the imitative signal generator 66 generates pulses each time that level is attained. Among these pulses, the

pulses which are not in accord with the resetting position or falling point of the saw-tooth waveform are taken as a fuel injection ending signal for ending the injection of fuel into the individual cylinders and this signal appears at the output terminal 6i.

Voltage waveforms appearing at various parts of the fuel injection ending signal generator 6 are shown in FIGS. 12a through 12e. FIG. 12a shows the voltage waveform of the fuel injection duration signal S for the specific cylinder supplied from the fuel injection duration signal generator 4. FIG. 1217 shows the voltage waveform of the saw-tooth wave V FIG. 12c shows pulses V obtained as a result of the detection of the end of the fuel injection duration signal S The pulses include a memory capacitor resetting pulse P and a setting pulse P FIG. 12d shows a rectangular waveform V which falls to the zero level at the time corresponding to the end of fuel injection into the individual cylinders. This rectangular waveform V, is subject to differentiation to appear as pulses V as shown in FIG. 12e so that the negative pulses among them are utilized as the fuel injection ending signal for supply to the individual cylinders.

The operation and detailed structure of the fuel injection ending signal generator 6 will be described with reference to FIGS. 9, 10 and 11. Referring to FIG. 9 showing the structure of the saw-tooth wave generator 60, it comprises a transistor 601 disposed in the discharging path of a capacitor 604 across which a sawtooth wavc appears, a leakage resistor 603, a transistor 605 which conducts for a very short period of time for charging the capacitor 604 in response to the application of the fuel injection starting signal S, from the fuel injection starting signal generator 2 to the input terminal 6a, a bias resistor 619 for normally keeping the transistor 605 in the non-conducting state, emitter follower transistor 606 and 607, a load resistor 608 for the transistor 607, resistors 609 and 611 and capacitors 610 and 612 constituting an integrator, an emitter follower transistor 613 for amplifying the output from the integrator, a load resistor 614 for the transistor 613, a differential amplifier 615 for comparing the output from the integrator with a reference voltage given by a variable resistor 617, a feedback resistor 616, a coupling resistor 618, and an output terminal 6b from which the saw-tooth waveform V, is delivered.

In operation, the transistor 60S conducts to charge the capacitor 604 up to a power supply voltage in response to the application of a pulse of the fuel injection starting signal Sy to the input terminal 6a from the fuel injection starting signal generator 2. The pulse of the fuel injection starting signal S, disappears soon and the transistor 605 is cut off. In the meantime, current which is dependent upon the output from the differential amplifier 615 is supplied to the transistor 601, and as a result, discharge takes place in the capacitor 604. By maintaining constant current supplied to the transistor 601 from the differential amplifier 615, a linearly decreasing V, as shown in FIG. 12b appears across the capacitor 604. The capacitor 604 is reset as the next pulse of the fuel injection starting signal S, is applied to the input terminal 6a, thence to the base of the transistor 605 after a short while. The voltage across the capacitor 604 is subject to impedance conversion by the transistors 606 and 607 so that a saw-tooth waveform voltage of low impedance appears across the load resistor 608. This saw-tooth waveform is integrated and smoothed out by the integrator composed of the resistors 609, 611 and the capacitors 610 and 612 and is then subject to impedance conversion by the transistor 613 again. Therefore, a dc. voltage proportional to the magnitude of the saw-tooth waveform appears across the resistor 614. The differential amplifier 615 compares this dc. voltage with the reference voltage supplied from the variable resistor 617 to deliver an output representative of the difference between these two voltages. This differential voltage is applied to the base of the transistor 601 so as to reduce the differential voltage. As a result, the magnitude of the saw-tooth waveform voltage appearing across the resistor 608 can be maintained constant. It will thus be understood that a saw-tooth waveform voltage V; of constant magnitude as shown in FIG. 12b can be generated in synchronism with the rotation of the engine and the magnitude is independent of the number of revolutions per unit time of the engine.

FIG. 10 shows the structure of the detector 63 for detecting the end of the fuel injection duration signal for the specific cylinder delivered from the fuel injection duration signal generator 4. Referring to FIG. 10, the detector 63 comprises a first differentiator composed of a capacitor 631 and a resistor 632, a first differentiated pulse amplifying transistor 633, a load resistor 634 for the transistor 633, a second differentiator composed of a capacitor 635 and a resistor 636, a second differentiated pulse amplifying transistor 637, a loat resistor 638 for the transistor 637, a third differentia J. composed of a capacitor 639 and a resistor 640, a third differentiated pulse amplifying transistor 641, a load resistor 642 for the transistor 641, a phase inverting transistor 643, a load resistor 644 for the transistor 643, an input terminal 6k, and output terminals 6c and 6d.

In operation, the fuel injection duration signal for the specific cylinder supplied from the fuel injection duration signal generator 4 to the input terminal 6k disappears at time to in FIG. 12a and a negative pulse produced by the capacitor 631 and the resistor 632 constituting the first differentiator is applied to the base of the transistor 633 at this moment to cut off the transistor 633. In response to the cut-off of the transistor 633, a positive pulse appears across the load resistor 634 for the transistor 633. The rising point of the positive pulse is detected by the capacitor 639 and the resistor 640 constituting the third differentiator and the pulse is amplified by the transistors 641 and 643 so that a pulse P A appears at the output terminal 60. The falling point of the positive pulse appearing across the load resistor 634 for the transistor 633 is subsequently detected by the capacitor 635 and the resistor 636 constituting the second differentiator and the pulse is amplified and subjected to inversion in sign by the transistor 637 so that a pulse P appears at the output terminal 6d with a slight delay relative to the pulse P as shown in FIG. 12c.

Referring to FIG. 11 showing the structure of the imitative signal generator 66, it comprises a coupling resistor 661, a comparator 662, a coupling resistor 663, an amplifying and inverting transistor 664, a load resistor 665 for the transistor 664, a coupling resistor 666, a NAND circuit 667, a coupling resistor 668, an amplifying and inverting transistor 669, a load resistor 670 for the transistor 669, a coupling resistor 671, a transistor 672 disposed in the charging circuit for a memory capacitor 673, a resetting transistor 674, a bias resistor 675 for the transistor 674, an amplifying transistor 676 of emitter follower configuration. a load resistor 677 for the transistor 676, coupling resistors 678 and 679, a comparator 680, a coupling resistor 681, an amplifying and inverting transistor 682, a load resistor 683 for the transistor 682, and a capacitor 687 and a resistor 686 constituting a differentiator. Input terminals 60 and 6f are connected to the output terminal 612 of the sawtooth wave generator 60 shown in FIG. 9 so that the saw-tooth waveform V, shown in FIG. 12b is applied to the input terminals 6e and 6ffrom the saw-tooth wave generator 60. Another input terminal 6;; is connected to the output terminal 60 of the detector 63 shown in FIG. so that the pulse P shown in FIG. 120 is applied to the input terminal 6g from the detector 63. A further input terminal 611 is connected to the output terminal 6d of the detector 63 shown in FIG. 10 so that the pulse P shown in FIG. 120 is applied to the input terminal 6n from the detector 63.

In operation, the transistor 674 conducts in response to the application of the pulse P to the input terminal 6g and the capacitor 673 discharges across the collector and emitter of the transistor 674. With the decrease in the voltage across the capacitor 673, the emitter voltage of the emitter follower transistor amplifier 676 is also decreased and the decreased emitter voltage is applied to one of the input terminals of the comparator 662 through the resistor 678. On the other hand, the saw-tooth waveform voltage V delivered from the sawtooth wave generator 60 is applied to the input terminal 62, thence to the other input terminal of the comparator 662 through the resistor 661, and the saw-tooth waveform voltage V,is compared with the emitter voltage of the transistor 676 in the comparator 662. Since, in this instance, the capacitor 673 is discharging through the transistor 674, the comparator 662 delivers a voltage instructing the charging of the capacitor 673 through the transistor 664, NAND circuit 667 and transistors 669 and 672. However, the NAND circuit 667 does not instruct the charging of the capacitor 673 since the pulse P,, is not applied to the input terminal 611 yet at this time. The NAND circuit 667 instructs the charging of the capacitor 673 as soon as the pulse P,, is applied to the input terminal 611 and the NAND logic of the NAND circuit 667 holds. Since the pulse P has disappeared at this time, the transistor 674 has been already cut off, and therefore, the capacitor 673 is charged through the transistor 672. The voltage appearing across the capacitor 673 is applied through the emitter follower transistor amplifier 676 to the input terminal of the comparator 662 to be compared with the saw-tooth waveform voltage V applied to the other terminal of the comparator 662. When these two voltages are equal to each other, the comparator 662 applies instructions to the NAND circuit 667 through the transistor 664 so as to stop the charging of the capacitor 673. Consequently, the transistor 672 is cut off immediately and the charging of the capacitor 673 is ceased. After a short while, the pulse P disappears. The capacitor 673 would not be charged again even when the voltage across the capacitor 673 may become lower than the saw-tooth waveform voltage V, unless the next pulses P and P are applied to the respective input terminals 6g and 6h again. Thus, the capacitor 673 is neither charged nor discharged and the voltage thereacross is maintained at a fixed level. In other words, the capacitor 673 stores therein a fixed level V,,-, (FIG. 12b) of the saw-tooth waveform voltage V corresponding to the end (at time 1,, in FIG. 12a of the fuel injection duration signal V, for the specific cylinder shown in FIG. 12a. Further, the voltage across the memory capacitor 673 is applied to one of the input terminals of the comparator 680, while the saw-tooth waveform voltage V is applied to the other input terminal of the comparator 680 through the input terminal 6f. After the voltage across the capacitor 673 has attained the fixed level, the saw-tooth waveform is reset again and then the saw-tooth waveform voltage V, attains a level equal to the voltage level-across the capacitor 673 again. At this point, the comparator 680 acts to urge the transistor 682 from the cut-off to the conducting state. In this manner, a rectangular waveform V,; as shown in FIG. 12d can be obtained, and the end of the fuel injection into each of the cylinders other than the specific cylinder can be detected. This end lies in the same angular position of rotation of the engine crankshaft as the end of the fuel injection duration signal for the specific cylinder and is in synchronism with the rotation of the engine. The rectangular waveform V,; is differentiated by the differentiator composed of the capacitor 687 and the resistor 686 to obtain positive and negative pulses, and the negative pulses V shown in FIG. 12e responsive to the transition of the transistor 687 from its cut-off to conducting state are selectively drived from the output terminal 6i to utilize same a fuel injection ending signal for the cylinders other than the specific cylinder. It will thus be understood that the fuel injection ending signal for the cylinders other than the specific cylinder is produced on the basis of the fuel injection duration signal for the specific cylinder and this fuel injection ending signal is successively distributed so that the duration of fuel injection can be rendered entirely the same for all the cylinders.

The fuel injection ending signal distributor 8 has a structure as shown in FIG. 13 and is actually a sort of a ring counter. The fuel injection ending signal distributor 8 comprises fuel injection ending signal distributor sections 81, 82, 83 and 84 for the first, second, third and fourth cylinders, respectively. The fuel injection ending signal for the specific cylinder derived from the detector 63 of the fuel injection ending signal generator 6 is applied to an input terminal 8A, while the injection interruption pulse from the imitative generator 66 of the fuel injection ending signal generator 6 is applied to an input terminal 88. The fuel injection ending signal distributor 8 has four output terminals 8a. 8b, 8c and 8d. A diode 81a is connected to the input terminal 8A, while diodes 82a, 83a and 84a are connected to the input terminal 88. The fuel injection ending signal distributor section 81 includes a resistor 81b grounded at one end thereof, a resistor 810, a silicon controlled rectifier-81d, a load resistor 81e for the silicon controlled rectifier 81d, and a capacitor 81f connected between the anode of the silicon controlled rectifier 81d and ground. The fuel injection ending signal distributor section 82 includes resistors 82b and 82c, a silicon controlled rectifier 82d, a load resistor 82e for the silicon controlled rectifier 82d, a capacitor 82f connected between the anode of the silicon controlled rectifier 82d and ground, and a capacitor 82g connected between the gate of the silicon controlled rectifier 82d and the junction point between the diode 82a and the resistor 

1. A system for electrically controlling fuel injection in a multi-cylinder internal combustion engine comprising in combination: a first starting signal generator for generating a first fuel injection starting signal at a predetermined angle in each cycle of operation of a selected reference cylinder, said starting signal being generated in synchronism with the rotation of said engine, a second starting signal generator for generating a plurality of succeeding fuel injection starting signals in synchronism with the rotation of said engine, each of said succeeding fuel injection starting signals defining the time at which fuel injection to a corresponding one of the remaining cylinders in said engine is initiated, a duration signal generator connected to said first starting signal generator for generating a fuel injection duration signal, said signal having a time duration proportional to the quantity of fuel to be injected into said cylinders, an ending signal generator connected to said second starting signal generator and to said duration signal generator for generating fuel injection termination signals, each of said signals defining the time at which fuel injection to a corresponding one of the cylinders is terminated, said ending signal generator comprising means for generating a saw-tooth waveform in synchronism with said succeeding fuel injection starting signals, means responsive to said duration signal for generating a duration signal termination signal, and means responsive to said saw-tooth waveform and said duration termination signal for generating fuel injection termination signals for each of said cylinders, a fuel injection termination signal distributor connected to said ending signal generator for distributing said fuel injection termination signals successively to each of said cylinders in a predetermined order, and a starting signal distributor connected to said first and second starting signal generators for distributing said succeeding fuel injection starting signals to said cylinders in said predetermined order.
 2. A system for electrically controlling fuel injection in a multi-cylinder internal combustion engine comprising: a first starting signal generator for generating a first fuel injection starting signal at a predetermined angle in each cycle of operation of a selected reference cylinder, said starting signal being generated in synchronism with the rotation of said engine, a second starting signal generator for generating a plurality of succeeding fuel injection starting signals in synchronism with the rotation of said engine, each of said succeeding fuel injection starting signals defining the time at which fuel injection to a corresponding one of the remaining cylinders in said engine is initiated, a duration signal generator connected to said first starting signal generator for generating a fuel injection duration signal, said duration signal having a time duration which varies with at least one operating parameter of said engine, an ending signal generator connected to said second starting signal generator and said duration signal generator for generating fuel injection termination signals, each of said termination signals defining the time at which fuel injection to a corresponding one of the cylinders is terminated, said ending signal generator comprising means for generating a saw-tooth waveform in synchronism with said succeeding fuel injection starting signals, means responsive to said duration siGnal for generating a duration signal termination signal, and means responsive to said saw-tooth waveform and said fuel injection termination signal for memorizing the level of said saw-tooth waveform when said termination signal for said selected reference cylinder is generated, and means for generating said fuel injection termination signals for each of said succeeding cylinders when the saw-tooth waveform reaches said memorized level, a fuel injection termination signal distributor connected to said ending signal generator for distributing said fuel injection termination signals successively to each of said cylinders in a predetermined order, and a starting signal distributor connected to said first and second starting signal generators for distributing said succeeding fuel injection starting signals to said cylinders in said predetermined order.
 3. The system as recited in claim 1, in which said first starting signal generator comprises means for generating a signal at a predetermined position in the operating cycle of the specific cylinder, and means for subjecting said signal to wave shaping to obtain a pulse signal.
 4. The system as recited in claim 1, in which said second starting signal generator comprises means for generating a signal at a predetermined position in the operating cycle of the individual cylinders, and means for subjecting said signal to wave shaping to obtain a pulse signal.
 5. The system as recited in claim 1, in which said duration signal generator comprises means for generating a saw-tooth waveform having a fixed time constant in response to the application of a pulse signal input, and means for generating a rectangular waveform the duration of which ranges from the rising point of said saw-tooth waveform to a point at which said saw-tooth waveform attains a predetermined level.
 6. The system as recited in claim 1, in which said ending signal distributor comprises a plurality of ending signal distributing means connected in cascade, the number of said distributing means being equal to the number of the cylinders, and said ending signal distributing means disposed in the first stage operates in response to a first input pulse signal, while the remainder of said ending signal distributing means disposed in the second and following stages operate sequentially in response to a second input pulse signal.
 7. The system as recited in claim 1, in which said starting signal distributor comprises a plurality starting signal distributing means connected in cascade, the number of said distributing means being equal to the number of the cylinders, and said starting signal distributing means disposed in the first stage operates in response to a first input pulse signal, while the remainder of said starting signal distributing means disposed in the second and following stages operate sequentially in response to a second input pulse signal.
 8. The system as recited in claim 1, which comprises further a first discriminator for applying to said duration signal generator a signal generated by said second starting signal generator in a low speed range of the engine which is lower than a predetermined speed, and a second discriminator for producing a ending signal for the individual cylinders on the basis of the duration signal generated by said duration signal generator in the low speed range.
 9. The system as recited in claim 8, in which said first discriminator comprises a comparator for discriminating whether the speed of the engine is higher or lower than the predetermined speed, and a NAND circuit for controlling the passage of the input signal applied from said second starting signal generator depending on the result of discrimination by said comparator.
 10. The system as recited in claim 8, in which said first discriminator generates a high speed range signal or a low speed range signal by discriminating whether the speed of the engine is higher or lower than the predetermined speed, and said second discriminaTor operates in such a manner that, when applied with the high speed range signal, the input signal applied from sand ending signal generator appears at the output terminal as an output signal, while when applied with the low speed range signal, the input signal applied from said duration signal generator appears at the output terminal as an output signal.
 11. The system as recited in claim 8, which comprises further a third discriminator which, in response to the output signal delivered from said first starting signal generator and the output signal delivered from said fuel injection duration signal generator, selects the duration signal for the specific cylinder from the duration signal applied from said duration signal generator and detects the switching point of the duration signal so selected, and the output from said third discriminator is applied to said ending signal distributor to be utilized as a reference for the distribution of the ending signal.
 12. The system as recited in claim 11, in which said third discriminator comprises a bistable multivibrator which is reset by the input signal applied from said first starting signal generator and is triggered by the input signal applied from said duration signal generator.
 13. The system as recited in claim 8, which comprises a fuel injection circuit for producing a signal for the individual cylinders in response to the application of the output signals delivered from said ending signal distributor and said signal distributor.
 14. The system as recited in claim 13, in which said fuel injection circuit comprises a plurality of fuel injection means each including a solenoid operated fuel injection valve associated with the corresponding cylinder a control element for energizing said fuel injection valve, and another control element for deenergizing said fuel injection valve.
 15. The system as recited in claim 2, in which said first starting signal generator comprises: a first generator for generating a first signal at a predetermined position in the operating cycle of the specific cylinder, and first means connected in circuit with said first generator for producing the signal initiating the fuel injection starting timing for the specific cylinder by wave-shaping and differentiating said first signal, and said second starting signal generator comprises: a second generator for generating second signals each produced at a predetermined position in each of the operating cycles of the individual cylinders, and second means connected in circuit with said second generator for producing said starting signals for the individual cylinders by wave-shaping and differentiating said second signals.
 16. The system as recited in claim 2, in which said first starting signal generator comprises means connected in circuit with said second starting signal generator for producing said signal of said first starting signal generator in synchronism with a specific one of the starting signals of said second fuel injection starting generator corresponding to the specific cylinder.
 17. The system as recited in claim 2, in which said duration signal generator comprises: a saw-tooth wave generator connecting in circuit with said first starting signal generator for generating a saw-tooth waveform having a fixed gradient in response to application of the signal of said first starting signal generator, and means connected in circuit with said saw-tooth wave generator for generating said duration signal of a rectangular waveform, the duration of which ranges from the rising point of said saw-tooth waveform to a point where said saw-tooth waveform reaches a level determined by at least one operating parameter of the engine.
 18. The system as recited in claim 2, in which said ending signal distributor comprises: a plurality of ending signal distributing circuits which are connected one another in a ring counter mode and whose number is equal to the number of the cylinders, a predetermined specific one of said distributing circuits having an input terminal connected in circuit to said ending signal generator for receiving the end signal for the specific cylinder and an output terminal connected in circuit to said fuel injection means, the remaining distributing circuits each having an input terminal connected in circuit to said fuel injection signal generator together with the input terminals of the other remaining distributing circuits for receiving the end signals for the individual cylinders and an output terminal connected in circuit individually to said fuel injection means, each of said distributing circuits being switched upon application of one of the ending signals to its input terminal, from a first state to a second state thereby producing at its output terminal an output signal indicative of the fuel injection ending time of the corresponding one of the cylinders only when the preceding distributing circuit is at the second state, and being switched from the second state to the first state when the succeeding distributing circuit is switched from the first state to the second state.
 19. The system as recited in claim 2, in which said starting signal distributor comprises: a plurality of starting signal distributing circuits which are connected one another in a ring counter mode and whose number is equal to the number of cylinders; a predetermined specific one of said distributing circuits having an input terminal connected in circuit to said first starting signal generator for receiving the starting signal for the specific cylinder and an output terminal connected in circuit to said fuel injection means, the remaining distributing circuits each having an input terminal connected in circuit to said second starting signal generator together with the input terminals of other remaining distributing circuits for receiving the starting signals for the individual cylinders and an output terminal connected in circuit individually to said fuel injection means, each of said distributing circuits being switched upon application of one of the starting signals to its input terminal, from a first state to a second state thereby producing at its output terminal an output signal indicative of the fuel injection starting time of the corresponding one of the cylinders only when the preceding distributing circuit is at the second state, and being switched from the second state to the first state when the succeeding distributing circuit is switched from the first state to the second state.
 20. The system as recited in claim 2, further comprising: a first discriminator connected in circuit between said second starting signal generator and the input terminal of said duration signal generator for applying the starting signals for the individual cylinders to said duration signal generator when the engine speed is lower than a predetermined value, whereby said duration signal generator generates the fuel injection duration signals for the individual cylinders on the basis of said starting signals applied thereto, and further generating a high speed signal when the engine speed is higher than said predetermined value, a second discriminator connected in circuit with said duration signal generator for producing signals on the basis of said fuel injection duration signals for the individual cylinders, said signals being applicable to said ending signal distributor in place of said ending signals produced by said ending signal generator, said second discriminator further connected in circuit between said fuel injection ending signal generator and said fuel injection ending signal distributor and in circuit with said first discriminator for applying said signals produced by said ending signal generator from being supplied to said ending signal distributor when said high speed signal is not applied thereto, and for permitting said ending signals to be applied to said ending signal distributor when said high Speed signal is applied thereto.
 21. The system as recited in claim 20, further comprising: an r.p.m. detector connected in circuit with said second starting signal generator for producing a voltage signal proportional to the engine speed by detecting the number of said starting signals produced from said second starting signal generator, in which said first discriminator comprises: a comparator connected in circuit with said RPM detector for comparing said voltage signal with a reference voltage signal representative of said predetermined value of the engine speed, and for generating said high speed signal when said voltage signal is higher than said reference voltage signal, and generating a low speed signal when said voltage signal is lower than said reference voltage signal, a logical product circuit connected in circuit with said comparator and said second starting signal generator for applying said starting signals to said duration signal generator when said low speed signal and said starting signals are simultaneously applied thereto.
 22. The system as recited in claim 20, further comprising: a third discriminator connected in circuit between said duration signal generator and said ending signal distributor for applying an ending signal for the specific cylinder to said ending signal distributor, said ending signal for the specific cylinder being produced by detecting the falling point of said duration signal for the specific cylinder selected from said duration signals applied from said duration signal generator. 